02The ordinary rule
At 18, look at the child and the case separately.
For the child who turns 18, the administrative assessment ordinarily ends because turning 18 is a terminating event—unless the Registrar has accepted an age-18 extension application.
Services Australia, not AusChildSupport, records the event, makes the decision and issues the amended Formal Assessment. Turning 18 is not the only possible terminating event, but the wider list is outside this page’s focus.
Read sections 12 and 151B–151E of the Child Support (Assessment) Act
03Extension record
When an assessment can continue
The Registrar must be satisfied of each relevant condition. This page can help you identify the questions, but it cannot decide whether an application will be accepted.
- 01Age reached
- The child has turned 17.
- 02Case in force
- The relevant assessment, agreement or other qualifying arrangement is—or is likely to be—in force immediately before the 18th birthday.
- 03Education on the birthday
- The child is likely to be in full-time secondary education on their 18th birthday.
- 04Birthday within the year
- The 18th birthday occurs on or before the applicable last day of that secondary school year.
- 05Application timing
- The application is made before the 18th birthday. A late application is only a limited exceptional-circumstances possibility decided by the Registrar—not a fallback strategy.
Eligibility detail: DSS Guide 2.5.3 Governing law: sections 151B–151E
04Education boundary
“Full-time secondary” has a specific meaning.
The school determines whether the education it provides is full-time secondary education. The label on the institution is not enough by itself.
- School holidays that form part of the school year can still count.
- The last day is determined by the school and can be the later of the last day of classes or the child’s examination period.
- A TAFE, specialist school or other institution may provide secondary education; the course must actually qualify as full-time secondary education.
- Distance learning and some home-school arrangements may qualify, subject to the official criteria and relevant state law.
Unusual school-year cases
International school years and programs that span calendar years can require closer attention. The extension is generally bounded by the last applicable school day in the calendar year the child turns 18. Ask the school for its relevant class and examination dates, then confirm the position with Services Australia.
Read the DSS examples and definitions05Identify the pathway
Assessment or agreement?
Start by identifying what is in force. Agreement wording and the way the case began can change who signs, what can continue and which end date controls.
01 · Administrative assessment
Services Australia calculated the liability
The parent or non-parent carer entitled to child support may apply for the age-18 extension. The person who pays cannot make that ordinary assessment application.
02 · Agreement modifying an assessment
An assessment existed before the agreement
The entitled carer may apply to extend the assessment. Whether the agreement continues to affect the amount depends on its terms, including any specific end date.
03 · Agreement initiated the case
There was no earlier assessment
Both parents generally need to sign the written extension application. An agreement’s specific end date can prevent or limit continuation.
Detailed agreement distinctions
If an agreement modified an existing assessment
If the agreement ends at 18, the agreement itself cannot be extended by the age-18 application, though the underlying assessment may be eligible to continue. If its specific end date falls during an accepted extension, the agreement can stop modifying the assessment from that date and the formula may apply instead.
If the agreement initiated the child support case
Both parents must sign the written extension application. If the agreement specifies an end date, that date cannot be overridden by an extension application. Where it ends on or before 18, a new agreement or assessment may need to be put in place before the birthday if support is to continue through the administrative system.
Review the exact agreement and confirm the administrative path with Services Australia. Consider legal advice before interpreting, replacing or ending an agreement.
Read DSS Guide 6.4.2 on terminating agreements06Before the deadline
How to act before 18
Gather the facts Services Australia will need. Do not send personal information to AusChildSupport.
- Confirm the child’s 18th birthday.
- Confirm whether the child will be in full-time secondary education on that date.
- Ask the school for the applicable last day of classes and examinations.
- Identify whether the case is an assessment, an agreement, or both.
- Contact Services Australia or use the current official form.
- Keep a copy of the information supplied and the decision received.
07After administrative support
If the assessment is not extended
Administrative path
The assessment ordinarily ends for that child
Services Australia gives effect to the terminating event. Other eligible children can remain in the assessment, and no particular revised amount should be assumed.
Contact Services Australia about the caseCourt path
Adult child maintenance may be considered
A court may make an order where maintenance is necessary to enable the child to complete education or because of the child’s disability. It is a different legal process, is not automatic and may warrant legal advice.
Read the Court’s child support and maintenance guidance Understand when legal advice may helpNot applying for an available extension may affect Family Tax Benefit in some circumstances. Check the person’s situation with Services Australia; do not assume the child support and Family Tax Benefit rules are the same.
See the official Family Tax Benefit note08Focused answers
Common questions
Does child support always stop on the 18th birthday?
Turning 18 is ordinarily a terminating event for that child. It is not a terminating event at 18 if Services Australia has accepted an eligible application for the assessment or agreement to continue. Other terminating events can also apply.
Source: DSS Guide 2.6.3Can the parent who pays child support request the extension?
For an ordinary administrative assessment, the application is made by the parent or non-parent carer entitled to child support. A paying parent cannot make that application. Agreement cases can differ: both parents may need to sign where an agreement initiated the child support case, and parents can jointly make a new agreement where appropriate.
Source: DSS Guide 2.5.3What if the 18th birthday falls during school holidays?
A child may still be treated as being in full-time secondary education during a school holiday that forms part of the school year, including where they will return after the break. The school and Services Australia determine the relevant facts.
Source: Services Australia guidanceDoes university or TAFE automatically extend child support?
No. The age-18 extension is for full-time secondary education, not tertiary education. A TAFE or another institution may count only where it is providing qualifying full-time secondary education. University or other tertiary study does not itself extend an administrative assessment.
Source: DSS Guide 2.5.3What happens if the assessment includes younger children?
A terminating event for one child does not necessarily end the whole assessment. If other eligible children remain, Services Australia can amend the assessment to give effect to the change. This page cannot predict the recalculated amount.
Source: DSS Guide 5.5.3What if the application deadline was missed?
Do not assume a late application will be accepted. The Registrar may accept one only where exceptional circumstances justify applying after the birthday. Services Australia says those circumstances must be outside the applicant’s control and have prevented an earlier application. Contact Services Australia promptly about the actual situation.
Source: Services Australia guidanceDoes a child support agreement automatically continue?
No. The result depends on how the agreement relates to an assessment, whether it initiated the case, its own end-date terms and whether the required application has been signed. Review the agreement and confirm the process with Services Australia; legal advice may help if the wording has legal consequences.
Source: DSS Guide 2.5.3Can support continue because of disability?
Not automatically through the administrative age-18 extension. A court may make an adult child maintenance order where maintenance is necessary because of the child’s disability. That is a separate legal process and the court decides whether an order is appropriate.
Source: Federal Circuit and Family Court guidance09Evidence register
Official sources checked
Checked 2 August 2026
Primary Australian sources · links open the current official page
| Source | Authority | What it supports | Date checked |
|---|---|---|---|
| Child support when your child turns 18 | Services Australia | Practical deadline, study, agreement and application instructions | 2 Aug 2026 |
| Child over 18 in full time secondary education form (CS2716) | Services Australia | Current official extension form | 2 Aug 2026 |
| Child Support Guide 2.5.3 | Department of Social Services | Extension eligibility, timing, agreements and school-year rules | 2 Aug 2026 |
| Child Support Guide 2.6.3 | Department of Social Services | Turning 18 as a terminating event | 2 Aug 2026 |
| Child Support Guide 6.4.2 | Department of Social Services | Terminating events and child support agreements | 2 Aug 2026 |
| Child Support Guide 5.5.3 | Department of Social Services | Effect where other eligible children remain | 2 Aug 2026 |
| Child Support (Assessment) Act 1989 | Federal Register of Legislation | Governing rules: sections 12 and 151B–151E | 2 Aug 2026 |
| Child support and maintenance | Federal Circuit and Family Court of Australia | Administrative and adult-child-maintenance boundary | 2 Aug 2026 |
| Family Law Act 1975 | Federal Register of Legislation | Court powers and adult child maintenance: sections 66E and 66L | 2 Aug 2026 |
Your next step
Use the official path before the deadline.
Services Australia decides extension applications. Legal advice may help where an agreement or adult child maintenance is involved.